Texas crop farmers are advised to give serious consideration to rotating herbicides as the potential for resistance to certain compounds becomes more common, according to a Texas AgriLife Extension Service specialist.
"Weed resistance to some herbicides is affecting a large number of acres in the southeastern United States," said Dr. Paul Baumann at the recent Stiles Farm Field Day at Thrall, attended by more than 300 producers. "Glyphosate (i.e. Roundup) resistant Palmer amaranth pigweed and others have been documented in other parts of the country. The occurrence of these (glyphosate resistant) weeds has been very limited in Texas."
Another pigweed species, common waterhemp, has displayed resistance to glyphosate and several ALS inhibitor herbicides along the Texas Gulf Coastal region, Baumann said.
"My opinion, shared by many of my weed scientist peers in Texas, is that weed resistance has not been a major issue for us yet. This is because along with using Roundup or other glyphosate products, we also use soil-active chemistries, such as yellow herbicides in cotton (and other crops)."
Baumann said this has helped manage some of the resistance issues "by throwing different herbicide modes of action in the mix."
"No question, we will continue to see some weed resistance in Texas," Baumann said.
Farmers can guard against weed resistance issues by using alternatives to glyphosate or adding an additional herbicide in the program that has a different mode of action, controlling the targeted weeds.
"The point is, from a research standpoint, we have got to do two things: We have to look at alternative chemistries to see if they will perform, especially against pigweed or water hemp," he said. "We’ve got to do tests so that we can recommend to our growers methods to control these types of weeds. We also need to develop specific herbicide programs to keep from having resistance issues. If we continue to employ a single herbicide-use pattern, such as glyphosate products year after year on crop after crop, and not putting another herbicide chemistry in the program whether it be in corn or cotton, we will develop resistance issues."
Meanwhile, Dr. Tom Isakeit, AgriLife Extension Service plant pathologist, discussed experiments using flutriafol to combat cotton-root rot. Stressing that his work is only in the experimental phase and not approved for commercial use, Isakeit said results so far have generally been favorable.
"On dryland farms, we’ve been conducting experiments spraying the lower stem with the fungicide," he said. "With an experiment at the Stiles farm in 2009, a 2-ounce rate reduced the amount of root rot by more than 50 percent."
Isakeit said the treatment only protects the plant itself and doesn’t penetrate the soil and destroy the fungus. The cost is $20 an acre.
"So far, this is very promising work," he said. "But we need to complete more testing before this can be available for growers."
Dr. Gaylon Morgan, AgriLife Extension Service cotton specialist, said the Texas cotton crop is in "a whole lot better situation this year as opposed to 2009."
"We had 34 percent abandonment in Texas last year and only 3 percent this year," he said. "We’re looking forward to a good crop. This year the state is in good to very good condition with only about a third in fair condition, and five percent in poor condition. We’re pretty good overall."
Two $4,000 Stiles Farm Foundation scholarships were given to area students headed to college during the noontime program during the field day. Receiving scholarships were Weston Fisher (Milam County) and Helen Hardy (Williamson County).